1. Field of the Invention
The construction of road base courses often requires the addition of a chemical composition to the soil particles utilized in the base course in order to improve the physical characteristics of the base course. Characteristics of the base courses which are affected by stabilization are density, adhesion, and stability against moisture and temperature extremes. A base course that is not properly stabilized is subject to formation of pot-holes, wash-boarding, frost-boils, dry weather flaking and wet weather leaching.
2. Description of the Prior Art
Soil stabilization has been used for many years in construction of road base courses. Materials commonly used for this purpose include lime, calcium chloride, sodium silicates, chrome-lignin, a mixture of molasses and fuel oil, calcium acrylate, lignin sulfonate and other materials. Lime has been widely used for many years as a means for reducing the shrinkage and plasticity index of soils having clay or caliche binders. Calcium chloride assists in the compactive process, making it possible to obtain greater densities and greater strengths with normal compactive efforts.
A waste material from pulp mills which utilize the sulfite process for digesting wood chips or sawdust has also been used as a soil stabilizing material. This material, referred to herein as lignin sulfonate, is a sodium, calcium or ammonium lignin sulfonate which is produced in large volume by the sulfite pulping process. As pointed out above, lignin sulfonate has been used for many years as a stabilizing agent. However, it has not been widely accepted by the road building industry. One of the reasons for its lack of acceptance on anything but secondary and tertiary roads is the failure of untreated lignin sulfonate to be uniformly distributed, resulting in untreated pockets within the base course materials.
U.S. Pat. No. 1,075,856 describes the use of modified sulfite waste liquor in soil stabilization.
U.S. Pat. Nos. 865,578; 2,375,019 and 3,053,019 also describe soil stabilizing compositions utilizing waste sulfite liquors in various forms.
None of the prior art references provides a composition which includes dispersant additives to improve the distribution of the lignin sulfonate throughout the soil to be stabilized. Thus, it is apparent that there has been a need for a soil stabilizing composition having the improved properties obtained by the present invention.